JP2002356753A - Porous metallic sintered compact for wear resistant member, and wear resistant ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wear resistant ring (porous metallic sintered compact) which has desired boundary strength when subjected to casting in a piston and has excellent joinability to a piston material (aluminum alloy). SOLUTION: Austenitic stainless steel powder having a particle-size distribution capable of passing through a sieve of 60 mesh and incapable of passing through a sieve of 350 mesh is used to prepare the porous sintered compact of austenitic stainless steel which has 20-50% pores by area ratio and in which pores of >5 μm diameter among the pores comprise >=80% of the total pore area by area ratio. Machinability-improving fine particles composed of one or more kinds selected from MnS, CaF, BN and enstatite can be incorporated in an amount of 0.1-5% by mass. This sintered compact is subjected to casting in a piston.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous metal sintered body for a wear-resistant member which is used by being cast and encapsulated in a light alloy member, and particularly suitable for an aluminum alloy piston used in an internal combustion engine. The present invention relates to a wear ring made of a porous metal sintered body.

[0002]

2. Description of the Related Art In recent years, engines made of aluminum alloy have become popular for the purpose of reducing the weight and heat radiation of engines, and pistons are also made of aluminum alloy. On the other hand, with the demand for higher engine output, the engine is exposed to a higher temperature combustion environment, and the piston ring is also required to have severe wear resistance.

[0003] In response to such demands for improved wear resistance of piston rings, piston rings of high hardness have been used. Therefore, since the piston ring groove is hit by the end faces of the piston rings, there is a possibility that the piston ring groove is set or deformed in a normal aluminum alloy. In particular, the combustion pressure directly acts on the top ring of a diesel engine, so the impact of the piston ring is repeated on the top ring groove, and the set ring is easily worn. When wear occurs in the top ring groove,
Gas leakage and oil leakage occur, resulting in a decrease in engine output.

In order to solve this problem, a configuration has been proposed in which a wear ring made of a material having a higher strength than the piston material is fixed to the piston ring groove, and the piston ring is supported by the wear ring. For example, in a piston for a diesel engine, a niresist cast iron insert (wear ring) is cast in the top ring groove, and the wear ring prevents the wear of the piston ring groove when the piston slides in the cylinder. Things are mainstream.

However, the wear-resistant ring made of niresist cast iron is a cast product, so the material cost is high, the yield and cutting workability are poor, the cost is high, and the aluminized ring is used for improving the cast-in property. Processing becomes essential. In addition, the iron alloy has a problem that it has a high mass and an insufficient heat conductivity, which hinders high performance of the engine.

Japanese Patent Publication No. 57-32743 discloses that at least the top ring groove peripheral wall of a piston ring groove has N
An aluminum alloy piston in which a sintered alloy insert material consisting of i: 8 to 25%, Cu: 3.5 to 10%, and the balance substantially consisting of Fe has been proposed. In addition, JP-A-3-1390
No. 66 proposes a porous metal reinforcing material suitable for use by being cast into an aluminum alloy piston to improve wear resistance. This porous metal reinforcement is Ni,
Powder of an alloy comprising one or more selected from the group consisting of Co, Cr, Mo, Mn and W and iron, or Ni, C
A powder obtained by sintering a mixture of iron powder and an alloy powder comprising one or more selected from the group consisting of o, Cr, Mo, Mn, and W, and iron, in a porous state. It is union. However, in the porous sintered body described in JP-A-3-139066, a large amount of alloying elements such as Ni, Co, Cr, and Mo are added, which is economically disadvantageous and causes the piston cast-in. There was a problem that the later groove workability deteriorated.

Japanese Patent Application Laid-Open No. 8-319504 discloses that Cr,
At least one of Mo, V, W, Mn, and Si is 2-70%;
The sintered body is made of iron-based raw material powder with 0.07 to 8.2% carbon and unavoidable impurity composition, and the hardness of the metal composed by cooling in gas and gas quenching is determined by micro Vickers hardness.
A metal sintered body composite material including a porous metal sintered body set to Hv 200 to 800 and a light metal impregnated into pores and solidified has been proposed. However, in the porous metal sintered bodies described in JP-A-3-139066 and JP-A-8-319504, a large amount of alloying elements such as Cr, Mo, and V are added so as to enable gas quenching. It is disadvantageous economically. There was also a problem that the groove workability after casting the piston was deteriorated.

Japanese Patent Application Laid-Open No. Hei 9-143639 discloses that
It is composed of a skeleton of 55% perforated Fe-based sintered alloy, and
A lightweight aluminum alloy piston body casting whose head is reinforced with a cast-in material consisting of a porous Fe-based sintered alloy having an overall specific surface area of 300 to 2000 cm ² / cm ³ and an overall porosity of 80 to 97% is proposed. Have been. However, when the piston is reinforced with the cast-in material disclosed in Japanese Patent Application Laid-Open No. 9-143639, there is a problem that the iron-based sintered alloy portion is as small as 3 to 20% and the wear resistance may be insufficient. Was.

Japanese Patent Application Laid-Open No. 2001-32747 discloses an internal combustion engine in which a supporting member made of an austenitic stainless steel porous body having a relative density of 50 to 80% and constituting a piston groove is cast in a main body. Aluminum alloy pistons have been proposed.

[0010]

As described above, Japanese Patent Publication No. 57-32743, Japanese Patent Application Laid-Open No. 3-139066, and Japanese Patent Application Laid-Open No.
By using a porous metal sintered body (sintered alloy) described in JP-A-319504 and JP-A-2001-32747, which is cast into an aluminum alloy piston and used, the abrasion resistance of the piston ring groove is ensured. To improve. However, when such a porous metal sintered body is cast into a piston, the boundary strength with the piston material (aluminum alloy) varies, and boundary delamination may occur, making it difficult to obtain a product having stable characteristics, and assuring quality. There was a problem. Further, in order to improve the wear resistance of light alloy members, not limited to aluminum alloy pistons, it is intended to cast such a porous metal sintered body into a light alloy member such as an aluminum alloy. However, in order to maintain stable boundary strength, there is a demand for a porous metal sintered body having excellent bonding properties with a light alloy member.

Further, the porous metal sintered body (sintered alloy) is
There is a problem that cutting workability is low. Porous metal sintered body has intermittent cutting because it has voids, high cutting resistance,
Since the life of the cutting tool (bite) is short, there is also a problem that the cutting efficiency is reduced due to the replacement of the cutting tool, and the production cost is increased. The present invention advantageously solves the above-described problems of the prior art, and can stably secure a desired boundary strength when cast into a light alloy member such as an aluminum alloy, and has an excellent bondability with a light alloy member. An object of the present invention is to provide a porous metal sintered body for a wear member and a method for manufacturing the same. In particular, the present invention provides a porous metal sintered body which can stably secure a desired boundary strength when cast into an aluminum alloy piston, has excellent jointability with a piston material, or further has excellent cutting workability. An object of the present invention is to provide a ring made of anti-friction and a method of manufacturing the ring.

[0012]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have proposed a method of casting a piston material and a wear-resistant ring when cast into an aluminum alloy piston which is a kind of light alloy. The factors affecting the boundary strength were studied diligently.
In a conventional wear ring made of a porous metal sintered body, the porosity is generally regulated within a certain range in order to obtain a desired boundary strength with the piston material. To measure the porosity of a product, it is common to cut the product, take an image of the cross-sectional structure, and calculate by image analysis. However, such a method requires cutting the product. It cannot be applied to the production of some processes, and the measurement of the porosity is usually substituted by the density measurement.

First, the present inventors cast a porous iron-based sintered body having holes in a ring shape into an aluminum alloy piston, and then sampled a tensile test piece including a joint boundary. A tensile test was performed using these tensile tests to determine the boundary strength. The porosity of each porous iron-based sintered body was determined by density measurement. FIG. 3 shows the relationship between the boundary strength and the porosity. The boundary strength (σ) is the desired boundary strength (σ _E )
The ratio was expressed as the boundary intensity ratio σ / σ _E. This means that at a boundary strength ratio of 1 or more, the boundary strength σ becomes a value equal to or more than a desired boundary strength σ _E.

FIG. 3 shows that even at the same porosity, the boundary strength ratio varies greatly. This is presumably because the porosity was substituted for the density measurement, and the management of the porosity obtained by the density measurement alone does not represent a factor that affects the boundary strength of the wear ring. Thus, the present inventors
Examining the results of FIG. 3 in more detail, it can be seen that even with the same porosity,
In some cases, there is a great difference in the distribution and form of the pores, and it has been conceived that this greatly affects the boundary strength between the piston material and the porous metal sintered body. Even if the porosity is the same, the size and number of the holes are different, for example, as shown in FIG.
In the porous metal sintered body having a pore distribution in a cross section schematically shown in (b), the sintered body having the pore distribution in (b) has a larger boundary strength with the piston material. Was found. Furthermore, when pouring an aluminum alloy, if the pores of the porous metal sintered body (wear ring) are fine, it is difficult for the pores to be impregnated with the aluminum alloy. It was found that the aluminum alloy was not impregnated and significantly affected the decrease in boundary strength.

Therefore, the present inventors have further studied the cause of the formation of fine pores in the porous metal sintered body (ring ring). As a result, it has been found that the boundary strength ratio is greatly affected by the existence ratio of micropores existing in the porous metal sintered body, particularly micropores having a diameter of 5 μm or less. The ratio of the fine porosity having a diameter of 5 μm or less to the total porosity present in the porous metal sintered body, ｛(fine porosity of 5 μm or less in diameter) /
FIG. 1 shows the relationship between (total porosity)｝ × 100 (%) and the boundary strength ratio. From FIG. 1, it can be seen that fine porosity having a diameter of 5 μm or less existing in the porous metal sintered body was reduced by 20% to the total porosity.
By setting the ratio to less than 1, the boundary strength ratio becomes 1 or more. The boundary strength ratio is shown based on the strength (boundary strength σ _E ) obtained when an alfin treatment is applied to a two-resist cast iron wear ring. Here, a fine porosity of 5 μm or less in diameter,
The total porosity was obtained by polishing the cross section of the porous metal sintered body, measuring the area of the porosity in the cross section with an image analyzer, calculating each area ratio, and taking the value as the porosity.

Further, the formation of fine pores in the porous metal sintered body is greatly affected by the particle size distribution of the alloy powder used.
In particular, in order to reduce the porosity of fine particles having a diameter of 5 μm or less to less than 20%, it is necessary to prevent the alloy powder used from being mixed with a fine powder passing through a # 350 sieve (−350 mesh). did. The present invention is based on the above-mentioned findings,
It was completed after further consideration.

That is, the present invention relates to a porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder, wherein the porous metal sintered body has 20 to 50% of pores. A porous material for wear-resistant members excellent in bondability with a light alloy member, characterized in that the porosity is greater than 80% of the total porosity. It is a metal sintered body. The present invention also provides a wear-resistant ring made of a porous metal sintered body, wherein the porous metal sintered body has a porosity of 20 to 50% and has a diameter of 5 μm among the pores. Is a porous austenitic stainless steel sintered body having more than 80% of the total porosity with respect to the total porosity.
Further, in the present invention, the porous metal sintered body is preferably
C: 0.1 to 1.5%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, S: 0.03% or less, Ni: 5.0 to 15.0
%, Cr: 15.0 to 25.0%, and the balance is preferably a porous austenitic stainless steel sintered body having a composition of substantially Fe, and in the present invention, the porous metal sintered body But MnS, CaF ₂ , B with a particle size of 150 μm or less
N, and one or more kinds of fine particles for improving machinability selected from the group consisting of
It is preferred that the content be contained by mass%.

Further, the present invention provides a method for manufacturing a semiconductor device, comprising:
After mixing with a lubricant powder to form a mixed powder, the mixed powder is formed into a green compact, and then the green compact is sintered to form a porous metal sintered body. A method for manufacturing a body, wherein the alloy powder is an alloy powder having a particle size distribution of -60 mesh to +350 mesh, characterized in that the porous metal sintered body for wear-resistant members has excellent bondability with light alloy members. It is a manufacturing method of.

Further, the present invention provides a method for manufacturing a semiconductor device, comprising:
After mixing with the lubricant powder to form a mixed powder, the mixed powder is formed into a ring to form a green compact, and then the green compact is sintered to form a porous metal sintered body wear ring. The alloy powder is an austenitic stainless steel powder having a particle size distribution of −60 mesh to +350 mesh, and the mixed powder is 1.5% by mass or less of the graphite powder.
The present invention provides a method for producing a wear-resistant ring, characterized in that the lubricant powder is contained in an amount of 0.5 to 1.5% by mass, and the present invention further provides that the mixed powder further comprises MnS, CaF ₂ ,
BN, and a fine particle powder for machinability improvement consisting of one or more selected from enstatite, 0.1%
In the present invention, the austenitic stainless steel powder preferably contains
C: 0.3% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, S: 0.03% or less, Ni: 5.0 to 15.0
%, Cr: 15.0 to 25.0%, and the balance is preferably austenitic stainless steel powder having a composition of substantially Fe.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A wear-resistant member such as a wear-resistant ring is made of a porous metal sintered body to be a product as it is, and is cast in a light alloy member such as an aluminum alloy piston.
Finished, etc., before use. For example, in the case of a piston for an internal combustion engine, after being cast into an aluminum alloy piston, the piston ring groove and oil ring groove and the like are finished, and the piston ring and oil ring are attached, and the wear ring is used for use. Offered.

In the porous metal sintered body for a wear-resistant member of the present invention, it is not necessary to particularly limit the material, and any material usually used for a wear-resistant member is suitable. It can be selected as appropriate according to the location to be performed. Further, the porous metal sintered body for a wear-resistant member of the present invention, the area ratio is 20 to
Has 50% vacancies. If the porosity is less than 20%, when cast into a piston made of a light alloy such as an aluminum alloy, the molten metal of the light alloy such as an aluminum alloy does not impregnate the pores of the wear ring, and the boundary strength decreases. On the other hand, if the porosity exceeds 50%, the porosity is too large, the strength is reduced, and the porosity is deformed during operation. For this reason, the porosity of the porous metal sintered body for wear-resistant members is 20 to 50
%.

Further, the porous metal sintered body for a wear-resistant member of the present invention has at least 80% of pores having a diameter exceeding 5 μm with respect to the total porosity. If the porosity exceeding 5 μm in diameter is less than 80% of the total porosity, that is, 5 μm in diameter
When the following porosity exceeds 20% of the total porosity, the number of fine porosity increases, and as shown in FIG. 1, the boundary strength decreases when the boundary strength ratio is less than 1. For this reason, the porosity exceeding 5 μm in diameter is limited to 80% or more of the total porosity.

According to the present invention, in the wear-resistant ring of the present invention, which is a wear-resistant member, the porous metal sintered body constituting the wear-resistant ring is made of an austenitic stainless steel sintered body (porous austenitic sintered body containing pores having the above-described structure. Stainless steel sintered body). In the present invention, in order to prevent the generation of cracks at the interface between the piston and the wear ring, a material having a thermal expansion coefficient difference as small as possible from the aluminum alloy as the piston material is used for the wear ring. It is necessary to minimize the thermal stress generated during the process. Therefore, it is preferable to use an austenitic stainless steel sintered body as the wear-resistant material. The coefficient of thermal expansion of austenitic stainless steel is about 16 × 10-6 to 18 × 10-6 / ° C, and the coefficient of thermal expansion of aluminum alloy (20 × 10-6 / ° C)
Close to.

The porous austenitic stainless steel sintered body constituting the wear-resistant material has a C content of 0.1 to 1.5% by mass.
%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, S: 0.03% or less, Ni: 5.0 to 15.0%, Cr: 15.0 to 2
It is preferable to have a composition containing 5.0%, with the balance being substantially Fe. Next, the reason for limiting the composition of the austenitic stainless steel sintered body will be described.

C: 0.1 to 1.5% C is an element that increases the strength and hardness of the sintered body. In the present invention, the content of 0.1% or more is required for securing the strength and improving the wear resistance. If the content exceeds 1.5%, the carbides become coarse and the machinability decreases. Therefore, C is 0.1 to
Preferably, it is limited to 1.5%.

Si: 1.0% or less Si is an element that increases the strength of the sintered body, and is preferably contained at 0.3% or more. However, if it exceeds 1.0%, the sintered body tends to become brittle. Become. Therefore, Si is 1.0
% Is preferable. Mn: 2.0% or less Mn is an element that increases the strength of the sintered body, and is preferably contained in the present invention in an amount of 0.05% or more, but if it exceeds 2.0%, the sintered body becomes brittle. It becomes a tendency. For this reason, Mn is preferably set to 2.0% or less.

P: not more than 0.1% When P is contained in an amount exceeding 0.1%, the amount of steadite carbide increases and the machinability decreases. For this reason, P is preferably limited to 0.1% or less. In addition, more preferably 0.05%
It is as follows. S: 0.03% or less S forms sulfide, and it is preferable to reduce as much as possible to reduce ductility and toughness of the material. For this reason, in the present invention, S is preferably set to 0.03% or less.

Ni: 5.0 to 15.0% Ni is an austenitizing element, and is preferably contained in the present invention in an amount of 5% or more. On the other hand, if the content exceeds 15.0%, the hardness decreases. Therefore, Ni is 5.0-15.0%
It is preferable to limit to the range. Cr: 15.0 to 25.0% Cr is a solid solution strengthening element, and is preferably contained at 15.0% or more in order to secure a desired strength. On the other hand, if the content exceeds 25.0%, precipitation of Cr carbide on the grain boundaries becomes remarkable, and the wear resistance decreases. Therefore, Cr is 15.0-25.0%
It is preferable to limit to the range.

In addition to the above-mentioned components, there is no problem if one or more of Mo, Ti and Nb are contained in a total of 1% or less. The balance other than the above components is substantially Fe. As inevitable impurities, N: 0.1% or less, S
e: 0.15% or less is acceptable. Incidentally, the porous metal sintered body constituting the wear ring of the present invention, in the matrix of the austenitic stainless steel composition described above, for improving machinability, it is preferable to disperse fine particles for machinability improvement. . As fine particles for improving machinability to be dispersed, MnS, CaF ₂ , B
It is preferable to use one or more selected from N and enstatite. MnS, CaF ₂ , BN, and enstatite are all particles that improve machinability, and can be selected and contained as needed.

By uniformly dispersing the fine particles for improving machinability in the matrix, the chips during cutting are divided into a size determined by the distance between these fine particles. Therefore, the cutting resistance is kept low. The fine particles for improving machinability dispersed in the matrix have a particle size of 150 μm.
It is preferable to use fine particles of m or less. When the particle size of the fine particles exceeds 150 μm, the boundary strength decreases. In addition,
Preferably it is 5 to 100 μm.

The content of the fine particles for improving machinability dispersed in the matrix of the wear ring is preferably 0.1 to 5% by mass. When the content of the fine particles for improving machinability is less than 0.1% by mass, the effect of improving machinability is not recognized. on the other hand,
If the content exceeds 5% by mass, the adhesion strength to the matrix decreases. Therefore, the fine particles for improving machinability having a particle size of 150 μm or less are preferably contained in the range of 0.1 to 5% by mass.

It is preferable that any one of the above-mentioned wear-resistant rings is cast into an aluminum alloy piston to make an aluminum alloy piston for an internal combustion engine. Next, a method for producing the porous metal sintered body for a wear-resistant member of the present invention will be described. After mixing the alloy powder, the graphite powder, and the lubricant powder as raw materials to form a mixed powder, the mixed powder is charged into a mold and pressed to form a green compact. Sintered to form a porous metal sintered body. As a raw material powder, the alloy powder to be used is passed through a 60-mesh sieve (hereinafter, also referred to as a 60-mesh under or -60 mesh) to obtain 350
It is preferable to use an alloy powder adjusted to a particle size distribution that does not pass through a mesh sieve (hereinafter also referred to as 350 mesh over or +350 mesh).

When particles of +100 mesh (not passing through a # 100 mesh sieve) are present, the compactability of the mixed powder is reduced, making it difficult to obtain a compact having a desired density, and shortening the mold life. However, if the size of the particles of -60 to +100 mesh is less than 40% of the whole powder, it can be molded, which is advantageous for obtaining a green compact having a desired porosity. On the other hand, when particles of −350 mesh (passing through a # 350 mesh sieve) are present, the amount of fine pores having a diameter of less than 5 μm increases, and the boundary strength ratio tends to decrease.

The type of the alloy powder used in the porous metal sintered body for wear-resistant members is not particularly limited. Depending on the use of the wear-resistant member, an alloy powder of an optimal material can be used as appropriate. In addition, it is preferable to use stainless steel powder from the viewpoint of oxidation resistance. Ferritic, austenitic and martensitic stainless steels are all suitable. It is preferable to appropriately adopt generally known conditions for the compacting conditions, the sintering conditions, and the like according to each wear-resistant member.

Next, the method for producing a wear-resistant ring of the present invention will be described. The wear ring is manufactured from a porous metal sintered body including the pores having the above-described configuration. The porous metal sintered body is obtained by mixing an alloy powder as a raw material, graphite powder, a lubricant powder, and a granulating agent to form a mixed powder, and then charging the mixed powder into a mold and pressing. Into a ring-shaped green compact,
The green compact is sintered to make a ring.

In the present invention, the alloy powder used as the raw material powder is austenitic stainless steel powder. As described above, the austenitic stainless steel powder used passes through a 60-mesh sieve (hereinafter, also referred to as 60-mesh under or -60 mesh) and does not pass through a 350-mesh sieve (hereinafter, 350-mesh over, Austenitic stainless steel powder adjusted to a particle size distribution is also preferable.

When particles of +100 mesh (not passing through a # 100 mesh sieve) are present, the compactability of the mixed powder is reduced, making it difficult to obtain a compact having a desired density, and further increasing the mold life. Although it may decrease, if the particle size of -60 to +100 mesh is less than 40% of the whole powder, it can be molded and is advantageous for obtaining a green compact having a desired porosity. . On the other hand, when particles of −350 mesh (passing through a # 350 mesh sieve) are present, the amount of fine pores having a diameter of less than 5 μm increases, and the boundary strength ratio tends to decrease.

The austenitic stainless steel powder includes SUS 302, SUS 303, SUS 304, SUS 304L, SUS 316,
SUS 317 and SUS 310S are preferred. Among them, SUS 303 and SUS 304, which have a high coefficient of thermal expansion, are preferably used as the material of the wear-resistant ring from the viewpoint of preventing the occurrence of cracks at the interface. With SUS 304, improvement in oxidation resistance and wear resistance can be expected.

The austenitic stainless steel powder having the above-mentioned particle size distribution is further mixed with graphite powder, a lubricant powder such as zinc stearate, a wax-based granulating agent or a fine powder for improving machinability. Make a mixed powder. Graphite powder is added as an alloy element to increase the strength of the porous sintered body, but its content in the mixed powder is 1.5% by mass.
If it exceeds, carbides will increase, impair the properties of the austenitic stainless steel, degrade machinability, generate a liquid phase at the time of sintering, generate many independent vacancies, and lower the boundary strength. For this reason, the graphite powder is preferably limited to 1.5% by mass or less. The particle size of the graphite powder is 0.1 to 10μ.
m is preferable. If it is less than 0.1 μm, handling becomes difficult, and if it exceeds 10 μm, uniform dispersion becomes difficult.

In the wear ring of the present invention, in addition to the composition of the mixed powder described above, the mixed powder may further contain fine particles for improving machinability in order to improve machinability. The fine particle powder for improving machinability is preferably one or more selected from MnS, CaF ₂ , BN, and enstatite. MnS, CaF ₂ , BN, and enstatite are all particles that improve machinability, and can be selected and contained as needed. Also, the fine particle powder for improving machinability added to the mixed powder is preferably a fine particle powder having a particle size of 150 μm or less. Fine particle size of 15
If it exceeds 0 μm, the boundary strength decreases. The thickness is preferably 5 to 100 μm.

When the mixed powder contains the fine particle powder for improving machinability, the content of the fine particle powder for improving machinability is 0.1%.
It is preferable to set it to 5 mass%. If it is less than 0.1% by mass, the effect of improving machinability is small, while if it exceeds 5% by mass, the boundary strength decreases. The above-mentioned mixed powder is charged into a metal mold and pressed to form an annular (ring-shaped) green compact. The method for molding the mixed powder is not particularly limited, but it is preferable to use a molding press or the like to form a thin ring.

The annular porous sintered body thus obtained is mounted on a portion corresponding to a ring groove of a mold for forming a piston, a molten aluminum alloy melt is poured into the mold, and high-pressure die-cast. Alternatively, a piston in which a sintered body is cast by squeezing a molten metal is manufactured. As a result, the molten metal penetrates into the pores of the sintered body, and the joining with the piston material is completed. Thereafter, the wear ring is subjected to a cutting process with a predetermined groove size.

[0043]

Example 1 Example 1 Austenitic stainless steel powder (SUS 304) was mixed with graphite powder, lubricant powder, or MnS powder as fine particles for improving machinability, followed by mixing and kneading. After forming the mixed powder, the mixture was filled in a mold and pressed by a forming press to obtain a ring-shaped green compact having a predetermined size. As shown in Table 1, the austenitic stainless steel powder was classified in advance to adjust the particle size distribution.

Next, these compacts were sintered at 1100 to 1200 ° C. to obtain a porous austenitic stainless steel sintered body having pores having the composition shown in Table 2. The total porosity is
Porosity was determined by density measurement. The density was measured by the Archimedes method. In addition, the ratio of the fine pores to the total pores is obtained by imaging the structure of the sintered body in the pressing direction with a metallographic microscope and analyzing the image by analyzing the total area of the fine pores having a diameter of 5 μm or less and the area of the total pores. Take, (diameter 5μ
It was determined by (total area of micropores not more than m) / (area of all pores). The number of measurement points was three on the circumference.

These sintered bodies are used as a ring for a piston mold.
It was attached to the groove equivalent part. Then, in the mold,
After injecting molten gold (JIS AC8A), forging
Then, it was finished into a piston shape of a predetermined size. Also obtained
Take a tensile test specimen from the piston, including the boundary with the wear ring.
Then, the boundary strength at the boundary was determined by a tensile test. Tension
The direction of specimen collection should be such that the boundary is perpendicular to the specimen axis.
The direction included. The boundary strength σ is the desired boundary strength.
σ _E, The boundary strength ratio σ / σ_EWas evaluated.

Further, a thermal shock test was carried out on a piston having a ring-proof ring. In this test, the lower part of the piston is immersed in a water tank, the upper part (the ring-resistant side) is heated with a burner for a certain time, and then the burner heating is stopped for a certain time.
This is a test in which heating and cooling are repeated 2000 cycles. The heating / cooling cycle consists of 60 cycles of 100 ° C-350 ° C-100 ° C.
s. After the test, a test piece was sampled from the boundary, and the presence or absence of cracks was examined. The sampling points of the test pieces were 20 / piece. If there are no cracks after 2,000 cycles under these conditions, engine tests have confirmed that there is no problem.

Table 2 shows the results.

[0048]

[Table 1]

[0049]

[Table 2]

Each of the examples of the present invention has a high boundary strength ratio of 1.0 or more, has no cracks at the boundary due to thermal shock, and has a high boundary strength. On the other hand, the comparative examples outside the range of the present invention have a low boundary strength ratio and many cracks are generated at the boundary. The comparative example was a wear-resistant ring having inferior bondability despite having the same porosity as the inventive example. (Example 2) Graphite powder, lubricant powder, or fine particles for improving machinability were added to austenitic stainless steel powder and mixed, kneaded to obtain a mixed powder, and then filled in a mold and molded. Press molding was performed by a press to obtain a ring-shaped green compact having a predetermined size. The austenitic stainless steel powder was classified in advance and adjusted to a particle size distribution of -60 mesh to +350 mesh. In addition, particles of -60 to +100 mesh accounted for 26% of the whole.

Next, these green compacts were sintered at 1100 to 1200 ° C. to obtain a porous austenitic stainless steel sintered body having pores having the composition shown in Table 3. The total porosity is
As in Example 1, the porosity was determined by density measurement. For these sintered bodies, a slipping wear test, a cutting tool wear test, and a thermal shock resistance were performed.

In the cutting tool wear test, the sintered body was made of BNX4 cutting tool material, the cutting speed was 250 m / min, and the cutting length was 2044 m.
Under the following cutting conditions, the wear amount of the cutting tool (bite) after cutting was measured, and the machinability was evaluated. The thermal shock resistance was determined by heating the sintered body to 500 ° C., immersing it in water, and visually measuring the number of cracks generated in the sintered body.

In the sliding tapping test, a test piece was sampled from a sintered body and tested as a piston side member (simulated wear ring) 13 of a tester (high temperature valve seat wear tester) 11 shown in FIG. Abrasion (abrasion amount of the simulated wear ring) was measured. The sliding tapping test means that a simulated wear ring 13 is fixed to the testing machine 11 so that it cannot move in the axial direction, and a ring material 12 equivalent to a piston ring is formed.
Is concentrically mounted on the simulated wear ring 13 and the cast iron rod 15 equivalent to the cylinder liner provided on the inner peripheral surface side of the ring material 12 is reciprocated in the axial direction. This is a test for imparting an operation mode in which the side member 13 is hit. The test machine 11 has a heater 14 for heating the test material,
It is possible to reproduce the high temperature state during combustion in the engine without actually burning the fuel, and it is possible to simulate the state change of the wear ring.

The test conditions were as follows. Piston side material temperature: 340 ° C Repetition rate: 1500 times / minute Rotation (ring material rotation speed): 3.0 rpm Surface pressure: 20 kg / cm ² Test time: 10h On the other hand, as the ring material 12, 17Cr stainless steel is gas-nitrided What was used was used.

As a conventional example, a niresist cast iron material was used. Table 3 shows the obtained results.

[0056]

[Table 3]

In the example of the present invention, there is no occurrence of cracks due to thermal shock, and the wear ring has less wear of the cutting tool than the conventional example and has excellent machinability. Further, it is shown that the ring is less wear due to a sliding tap test and has excellent wear resistance. On the other hand, the comparative examples out of the range of the present invention have a low boundary strength ratio, a large amount of cutting tool wear, and low heat shock resistance.

[0058]

According to the present invention, it is possible to stably produce a porous metal sintered body for a wear-resistant member having excellent bondability after casting, such as a wear-resistant ring, and the industrially remarkable effect is achieved. . In addition, the wear ring of the present invention has an excellent joining property at the time of cast-in, has excellent machinability, and has an effect that the cutting efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the ratio of micropores on the boundary strength ratio between a wear-resistant ring and a piston material after casting.

FIG. 2 is an explanatory view schematically showing an example of a distribution state of pores in a sintered body.

FIG. 3 is a graph showing a relationship between a porosity and a boundary strength ratio between a conventional wear-resistant ring and a piston material after cast-in.

FIG. 4 is a partially cutaway perspective view showing a testing machine for performing a property test of a wear ring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Crankcase 3 Piston 4 Liner 5 Water jacket 6 Cylinder liner 7 Piston ring 8 Ring groove 10 Wear ring 11 Test machine (High temperature valve seat wear test machine) 12 Ring material 13 Piston side material (simulated wear ring) 14 Heater 15 Cast iron rod

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 3/00 F02F 3/00 N 302 302Z F16J 1/01 F16J 1/01 9/26 9/26 A ( 72) Inventor Teruo Takahashi 1111 Nogi, Nogi-machi, Shimotsuga-gun, Tochigi Japan F-term in the Tochigi Plant of Piston Ring Co., Ltd. BA17 BA20 BB04 KA09 KA22

Claims (8)

[Claims] 1. A porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder, wherein the porous metal sintered body has a porosity of 20 to 50%. And the diameter of the holes is 5
A porous metal sintered body for wear-resistant members having excellent bondability with light alloy members, characterized by having porosity of more than 80 μm with respect to the total porosity. 2. A wear-resistant ring made of a porous metal sintered body, wherein said porous metal sintered body has a porosity of 20 to 50% and a diameter of said pores exceeds 5 μm. A wear-resistant ring comprising a porous austenitic stainless steel sintered body having pores of 80% or more of the total porosity. 3. The porous metal sintered body has a particle size of 150 μm.
The following m, MnS, CaF _2, BN, and enstatite one or for improving machinability fine particles composed of two or more species selected from among the tight claims, characterized in that it contains 0.1 to 5 wt% Item 3. A wear-resistant ring according to item 2. 4. The mass of the porous metal sintered body is as follows: C: 0.1 to 1.5%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, S: 0.03% or less, Ni: The wear-resistant ring according to claim 2, wherein the sintered body is a porous austenitic stainless steel sintered body having a composition of: 5.0 to 15.0%, Cr: 15.0 to 25.0%, and the balance being substantially Fe. . 5. An alloy powder, a graphite powder and a lubricant powder are mixed to obtain a mixed powder, and then the mixed powder is formed into a green compact, and then the green compact is sintered. A method of manufacturing a porous metal sintered body to be a porous metal sintered body, wherein the alloy powder is an alloy powder having a particle size distribution of -60 mesh to +350 mesh, For producing a porous metal sintered body for wear-resistant members having excellent resistance. 6. An alloy powder, a graphite powder and a lubricant powder are mixed to form a mixed powder, and then the mixed powder is formed into a ring to form a green compact. A method for manufacturing a wear-resistant ring made of a sintered porous metal sintered body, wherein the alloy powder is an austenitic stainless steel powder having a particle size distribution of −60 mesh to +350 mesh, and the mixed powder is the graphite. A method for producing a wear-resistant ring, comprising 1.5% by mass or less of powder and 0.5 to 1.5% by mass of the lubricant powder. 7. The fine particles for improving machinability, wherein the mixed powder further comprises one or more selected from MnS, CaF ₂ , BN and enstatite having a particle size of 150 μm or less. The method for producing a wear-resistant ring according to claim 6, wherein the powder contains 0.1 to 5% by mass. 8. The austenitic stainless steel powder is, by mass%, C: 0.3% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, S: 0.03% or less, Ni: 5.0 An austenitic stainless steel powder having a composition of about 15.0%, Cr: 15.0 to 25.0%, and the balance being substantially Fe.
Or the method for producing a wear-resistant ring described in 7 above.